Outputs a source level execution trace of a Ruby program.

It does this by registering an event handler with Kernel#set_trace_func for processing incoming events. It also provides methods for filtering unwanted trace output (see ::add_filter, ::on, and ::off).

Example

Consider the following ruby script

class A
  def square(a)
    return a*a
  end
end

a = A.new
a.square(5)

Running the above script using ruby -r tracer example.rb will output the following trace to STDOUT (Note you can also explicitly require 'tracer')

#0:<internal:lib/rubygems/custom_require>:38:Kernel:<: -
#0:example.rb:3::-: class A
#0:example.rb:3::C: class A
#0:example.rb:4::-:   def square(a)
#0:example.rb:7::E: end
#0:example.rb:9::-: a = A.new
#0:example.rb:10::-: a.square(5)
#0:example.rb:4:A:>:   def square(a)
#0:example.rb:5:A:-:     return a*a
#0:example.rb:6:A:<:   end
 |  |         | |  |
 |  |         | |   ---------------------+ event
 |  |         |  ------------------------+ class
 |  |          --------------------------+ line
 |   ------------------------------------+ filename
  ---------------------------------------+ thread

Symbol table used for displaying incoming events:

+}+

call a C-language routine

+{+

return from a C-language routine

+>+

call a Ruby method

C

start a class or module definition

E

finish a class or module definition

-

execute code on a new line

+^+

raise an exception

+<+

return from a Ruby method

by Keiju ISHITSUKA(keiju@ishitsuka.com)

Methods
A
O
S
Constants
stdout = STDOUT
 
verbose = false
 
display_process_id = false
 
display_thread_id = true
 
display_c_call = false
 
EVENT_SYMBOL = { "line" => "-", "call" => ">", "return" => "<", "class" => "C", "end" => "E", "raise" => "^", "c-call" => "}", "c-return" => "{", "unknown" => "?" }
 

Symbol table used for displaying trace information
Single = new
 

Reference to singleton instance of Tracer
Attributes
[RW] display_c_call

display C-routine calls in trace output (defaults to false)
[RW] display_c_call?

display C-routine calls in trace output (defaults to false)
[RW] display_process_id

display process id in trace output (defaults to false)
[RW] display_process_id?

display process id in trace output (defaults to false)
[RW] display_thread_id

display thread id in trace output (defaults to true)
[RW] display_thread_id?

display thread id in trace output (defaults to true)
[RW] stdout

output stream used to output trace (defaults to STDOUT)
[R] stdout_mutex

mutex lock used by tracer for displaying trace output
[RW] verbose

display additional debug information (defaults to false)
[RW] verbose?

display additional debug information (defaults to false)
Class Public methods
add_filter(p = proc)

Used to filter unwanted trace output

Example which only outputs lines of code executed within the Kernel class:

Tracer.add_filter do |event, file, line, id, binding, klass, *rest|
  "Kernel" == klass.to_s
end

Source: show | on GitHub 

# File lib/tracer.rb, line 271
def Tracer.add_filter(p = proc)
  Single.add_filter(p)
end
off()

Disable tracing

Source: show | on GitHub 

# File lib/tracer.rb, line 244
def Tracer.off
  Single.off
end
on()

Start tracing

Example

Tracer.on
# code to trace here
Tracer.off

You can also pass a block:

Tracer.on {
  # trace everything in this block
}

Source: show | on GitHub 

# File lib/tracer.rb, line 233
def Tracer.on
  if block_given?
    Single.on{yield}
  else
    Single.on
  end
end
set_get_line_procs(file_name, p = proc)

Register an event handler p which is called everytime a line in file_name is executed.

Example:

Tracer.set_get_line_procs("example.rb", lambda { |line|
  puts "line number executed is #{line}"
})

Source: show | on GitHub 

# File lib/tracer.rb, line 258
def Tracer.set_get_line_procs(file_name, p = proc)
  Single.set_get_line_procs(file_name, p)
end